Centrifugal disk filters typically use rapidly rotating filter elements contained in a pressure vessel to which a suspension of solid particles in a fluid are injected to effect separation and produce two streams exiting the unit. A clarified fluid represents one stream exiting the unit and a concentrated slurry or second phase represents the other stream.
Though the centrifugal disk filter provides an improved filtration method, the centrifugal filter has suffered from operational and durability problems. Centrifugal disk equipment typically has not been operable for extended periods of time without failure of the seals and/or bearings. As is typical of rotating equipment, seals and bearing surfaces should be relatively maintenance-free in order to be commercially viable. Seals are necessary to keep the slurry within the pressure vessel and to prevent the particulate from recontaminating the filtrate. Where hazardous substances are to be filtered, containment problems are critical in that leakage to atmosphere may be harmful to operators or other people in the area of the centrifugal disk filter. The prior centrifugal disk separators incorporated no means of detecting seal failure or of preventing such a failure from contaminating the filtrate. Most seal failures occur when abrasive material in the pressurized fluid being filtered enters into the mechanical seal, causing scarring of the seal faces which, in turn, then allows leakage.
The rotating equipment of the centrifugal filters must be properly aligned, balanced, and centered to provide smooth, vibration-free operation with proper sealing. Many types of couplings have been developed for similar applications but none have been successful at power transfer, quick separation, liquid transfer within a hollow interior, and liquid-tight connections at the same time.
Prior centrifugal filters incorporated a tapered or conical section to concentrate the heavier solids. Problems resulted from the turbulence created by vortex action of the filter so that the solids tended to circulate throughout the vessel, rather than being concentrated in the tapered section. The vortex action causes the fluid to fall on the interior wall of the vortex and rise at the peripheral wall. The rising liquid carries the solids back to the top and redistributes them throughout the fluid.